This invention relates to an outboard motor provided with a four-stroke engine and more particularly to an improved lubricating system for an internal combustion engine.
With engines embodying separating lubricating systems having separate oil reservoirs, such as are commonly employed with four-stroke engines, it is the practice to use a filtering screen on the oil pickup element that extends into the oil reservoir. The use of such screens is to remove foreign particles from the lubricant before it is delivered to the lubricating system of the engine. However, when such a lubricating screen is employed in conventional lubricating systems, it is necessary to remove the oil reservoir from the engine to afford access to the screen for its servicing and/or replacement.
The aforenoted problem is particularly acute if the engine is utilized in conjunction with an outboard motor. Outboard motors, due to their compact nature, make it very difficult to locate a suitably sized oil reservoir. Although it has been proposed to position the oil reservoir in the drive shaft housing portion of the engine and thus lower the center of gravity, this can complicate the problem in connection with servicing of a strainer in the oil reservoir.
It is, therefore, a principal object of this invention to provide an improved lubricating system for an internal combustion engine.
It is another object of this invention to provide a lubricating system for an internal combustion engine wherein the lubricant strainer may be serviced without necessitating removal of the lubricant sump from the engine.
It is a still further object of this invention to provide an improved lubricating system for the four-stroke cycle engine of an outboard motor that facilitates servicing.
As has been noted, when employing four-cycle engines in outboard motors, it is difficult to provide an adequate oil reservoir within the confined space. Previously proposed outboard motors using four-cycle engines have positioned the crankcase in the power head which thus substantially increases the height and raises the center of gravity of the outboard motor. Obviously, both of these results are undesirable. It has been proposed, as has been noted, to provide a separate oil reservoir that is located within the drive shaft housing. However, although this solves the aforenoted problems, it can present some problems of its own. For example, it is the normal practice to provide an external drain for the oil from the reservoir so that it can be replenished without having to disassemble the engine. However, the use of such external drains have presented the problem of sealing between the oil reservoir and the external drain of the drive shaft housing. In addition, the use of separate elements for this purpose complicates the overall structure. Such such separate oil reservoirs contained within the drive shaft housing can render some problems when servicing the engine and when considering vibration isolation.
It is, therefore, a still further object of this invention to provide an improved and simplified oil reservoir system for an outboard motor.
It is another object of this invention to provide an improved oil reservoir for an outboard motor that is formed integrally with the drive shaft housing.
Another problem attendant with the use of drive shaft housing positioned oil reservoirs for four-cycle engines is the arrangement for returning oil to the reservoir from a bypass valve. Normally, lubricating systems for engines include a pressure relief or bypass valve that returns oil to the oil reservoir when the pressure in the lubricating system exceeds a predetermined desired pressure. Where the oil reservoir is positioned within the drive shaft housing, this means that the pressure relief valve, which is normally positioned in the engine, must be provided with a drain that will permit oil to flow from the pressure relief valve back to the oil reservoir. However, the oil can return to the engine through such openings when the engine is tilted up and this is very undesirable.
It is, therefore, a still further object of this invention to provide an improved oil sump arrangement including a pressure return valve for an outboard motor.
It is another object of this invention to provide an oil relief system for an outboard motor wherein the relief valve is positioned remotely from the engine to facilitate servicing.